The invention relates in particular to a method for authorizing the use of a motor vehicle that has at least one first and a second antenna, wherein the first antenna and the second antenna are at a physical distance from one another, by means of a portable identification transmitter that has an identification transmitter antenna. The motor vehicle is preferably a two- or four-wheeled motor vehicle.
In a known method of this kind, it is desirable to improve it further against manipulations.
The object of the invention is in particular the provision of a method for authorizing the use of a motor vehicle having improved protection against manipulations.
The method according to the invention proceeds from a method for authorizing the use of a motor vehicle, in particular a two- or four-wheeled motor vehicle, that has at least one first and a second antenna, wherein the first antenna and the second antenna are at a physical distance from one another, by means of a portable identification transmitter that has an identification transmitter antenna.
This known method is developed according to the invention by the following steps.
In a first step, the first vehicle antenna emits a first signal that is received by the identification transmitter antenna.
In a second step, the identification transmitter ascertains at least one of the spatial components of the first electromagnetic field of the received first signal, preferably using an angle-resolving magnetic field sensor.
In a third step, the second vehicle antenna emits a second signal that is received by the identification transmitter antenna.
In a fourth step, the identification transmitter ascertains at least one of the spatial components of the second electromagnetic field of the received second signal, preferably using an angle-resolving magnetic field sensor.
In a fifth step, a first computer, preferably a computer in the identification transmitter, repeatedly ascertains, after a predetermined first time interval has elapsed, the angle at least between the ascertained spatial component of the first electromagnetic field of the received first signal and the ascertained spatial component of the second electromagnetic field of the received second signal.
In a sixth step, the identification transmitter repeatedly ascertains, after a predetermined time interval, preferably the predetermined first time interval, has elapsed, the field strength of at least the first electromagnetic field of the received first signal and, preferably repeatedly, also the field strength of the second electromagnetic field of the received second signal, wherein the ascertainment of the field strengths is preferably performed using the first computer.
In a seventh step, the identification transmitter sends an authorization signal to authorize the use of the motor vehicle to the motor vehicle only if the following prerequisites are cumulatively met:
the angle repeatedly ascertained each time after the predetermined first time interval has elapsed exceeds a predetermined threshold value,
the repeatedly ascertained angle increases or becomes greater, and/or
the repeatedly measured field strength of the first and/or second electromagnetic field likewise increases or becomes greater.
In summary, one aspect of the method according to the invention consists in ascertaining whether the identification transmitter moves toward the motor vehicle. This can firstly be established, according to the invention, by virtue of the identification transmitter repeatedly ascertaining the field strength of the signals that are emitted by the motor vehicle and checking whether the field strength or the field strengths increases or increase. This can secondly be established, according to the invention, by virtue of the identification transmitter repeatedly determining the angle between the signals emitted by the motor vehicle and checking whether the repeatedly determined angles increase.